1. Field of the invention
The present invention relates to valve systems for regulating aspiration events for fluid processing machines, such as for example internal combustion engines, compressors and pumps. More particularly, the present invention relates to rotary valve systems for regulating fluid intake and exhaust events of machines of the aforesaid type. Still more particularly, the present invention relates to a rotary valve system having a rotating orbiter disc having apertures therein for providing periodic alignments with intake and exhaust ports of the aforesaid type of machine, and one or more floater discs which provide selective modification of one or both the aforesaid alignments.
2. Description of the Related Art
All fluid processing machines, including machines operating on the basis of periodic compression of gases to provide mechanical energy, such as gasoline and diesel internal combustion engines, machines using mechanical energy to provide compression of gases, such as compressors for refrigeration, and machines using mechanical energy to move fluids, such as hydraulic pumps, require precise valve event regulation in order to function properly. The valves commonly used to provide control of the valve events are generally of two major conventional classes, poppet valves and rotary valves.
Poppet valves conventionally have a tapered ("mushroom" shaped) valve head connected with a rod. The rod is resiliently biased to abut a cam on a rotating cam shaft which causes the rod to periodically reciprocate in proportional to the speed of revolution of a drive shaft of the machine. Rod reciprocation provides movement of the valve head with respect to a seat formed at its respective port. When in its closed position, the valve head sealingly abuts the seat of the port, otherwise the valve head is separated from the seat, whereupon aspiration of a chamber fluidically communicating with the port is made possible.
While poppet valves are reliable, the valve head thereof tends to obstruct the port even when at a position furthest from the seat. The inherent collation of poppet valves also renders them difficult to keep cool. Poppet valves also generally require a variety of subcomponents, such as springs, guides, retainers, actuators, and seals. Also, the reciprocational movement of poppet valves introduces valve harmonics and valve "float" and limits valve response time, and consequently, engine speed and engine efficiency. Accordingly, in situations where poppet valves are inherently detrimental to efficient operation of the machine, rotary valves are an alternative.
Rotary valves are conventionally configured in the form of either a disc (as for example described in U.S. Pat. No. 4,418,658) or a cylinder (as for example described in U.S. Pat. No. 4,815,428), wherein the rotary valve rotates with respect to each seat of one or more ports of the machine. The rotary valve is provided with one or more apertures which, as the rotary valve rotates via a drive connected in time with the drive shaft of the machine, periodically align with a respective seat of one or more ports of a chamber of the machine. Whenever alignment occurs, the respective port and rotary valve aperture provide unobstructed aspiration of the chamber.
While fluid processing machines cover a wide variety of mechanisms, of particular interest is the internal combustion engine because it has become a world-wide ubiquitous source of motive power. Internal combustion engines may be of a reciprocating piston type or of a rotating piston type, wherein the reciprocating piston type is by far the most common of the two, principally because of its superior durability and relative ease of sealing. Internal combustion entries operate conventionally on either the Otto cycle (spark ignition) or the Diesel cycle (compression ignition).
The reciprocating internal combustion engine includes one or more piston-cylinder combinations which provide a combustion chamber for reciprocally driving the piston during combustion of an air/fuel mixture gas. The reciprocating internal combustion engine includes a block for providing placement of the one or more cylinders and for providing a mechanical linkage for converting reciprocation of the one or more pistons to rotation of a crank or drive shaft. The reciprocating internal combustion engine further includes a head connected with the block which provides a blind end of each cylinder that in part defines the combustion chamber thereof. Two or more ports for aspirating each combustion chamber are provided at the head, and a spark plug, with its associated ignition system, is provided with Otto cycle reciprocating internal combustion engines. In this regard, an intake manifold is connected with the head at one or more intake ports which provide air and, via fuel injectors or a carburetor, fuel into the combustion chamber; and an exhaust manifold is connected with the head at one or more exhaust ports which direct combusted gases from the combustion chamber.
Further, reciprocating internal combustion engines may operate on a four stroke or a two stroke cycle of operation.
Conventional four stroke cycle (Otto cycle) operation is schematically described as follows:
a) during an "intake stroke" the crank shaft revolves from 0 to 180 degrees, the exhaust port valve remains closed and the intake port valve is opened whereby the air/fuel gas mixture enters the combustion chamber as the piston descends from top dead center to bottom dead center;
b) during a "compression stroke" the crank shaft revolves from 180 to 360 degrees, the exhaust port valve remains closed and the intake port valve is closed whereupon the air/fuel gas mixture is compressed in the combustion chamber as the piston ascends from bottom dead center to top dead center;
c) during a "power stroke" the crank shaft revolves from 360 to 540 degrees, the exhaust port valve and the intake port valve remain closed whereupon the air/fuel gas mixture is ignited by the spark plug whereby the expansion of the gas causes the piston to descend from top dead center to bottom dead center; and
d) during an "exhaust stroke" the crank shaft revolves from 540 to 720 degrees, the intake port valve remains closed and the exhaust port is opened whereby the combusted air/fuel gas mixture leaves the combustion chamber as the piston ascends from bottom dead center to top dead center, whereupon the cycle repeats.
Of course, valve events may overlap and ignition timing may be advanced or retarded in order to fulfill one or more operational criteria of a particular engine.
Conventional two stroke cycle operation (having positive inlet pressure scavenging) is schematically described as follows:
a) during a first stroke the, crank shaft revolves from 0 to 180 degrees; as the piston ascends from bottom dead center, the air/fuel gas mixture enters under positive pressure into the cylinder via an open inlet port near bottom dead center whereby combusted gas within the cylinder is scavenged out an open exhaust port located further from bottom dead center than is the inlet port; as the piston ascends further, the inlet port is closed, and as the piston ascends still further, the exhaust port is closed; now compression of the air/fuel mixture gas occurs in the cylinder until the piston reaches top dead center; and
b) during a second stroke the crank shaft revolves from 180 to 360 degrees; a spark plug ignites the air/fuel mixture gas, whereupon the expansion of the gas causes the piston to descend; as the piston descends the exhaust port is opened and the combusted gas in part exits the cylinder through the exhaust port; as the piston reaches bottom dead center, the inlet port is opened, whereupon air/fuel mixture gas enters the cylinder and scavenges out the remaining combustion gas; the piston reaches bottom dead center, whereupon the cycle repeats.
Again, valve events and ignition timing my be timed otherwise in practice.
The four stroke cycle has the advantage of providing positive scavenging during the exhaust stroke, while the two stroke cycle has the advantage that each revolution of the crank shaft involves a power stroke.
Internal combustion engines are increasingly becoming subject to ever more stringent regulations concerning maximum acceptable pollutant emissions and minimum acceptable efficiency, while at the same time providing an acceptable level of output power and reasonable cost of production and operation.
Over the last quarter century, a proliferation of regulations, oil supply vulnerability, manufacturer competition, and increasing consumer sophistication have been driving forces behind ever improving engine technology. For example, today, as compared to twenty-five years ago, fuel efficiency has approximately doubled, and pollutant emissions (NO.sub.x, CO and HC) have been reduced by between seventy-five and ninety-five percent.
While increased fuel economy in vehicular applications is in some measure the result of reduced vehicle weight and aerodynamic vehicle design, in large measure improved fuel economy and reduced pollutant emissions are the result of electronic control over engine operation. In this regard, computer control of engine function is provided by an engine control module (ECM), wherein the ECM is provided with a number of sensors which serve to monitor various engine parameters, such as coolant temperature, engine speed, intake manifold pressure, intake air temperature, throttle position, as well as oxygen level in the exhaust to determine, and thereupon provide, instantaneous engine adjustments.
The ECM provides a basis for electronic fuel injection, which is far superior to carbureted fuel metering in that exactly the right fuel to air mixture is provided with each combustion stroke. The ECM further provides a basis for electronic ignition spark timing which is far superior to mechanical ignition systems because advancing or retarding of the spark is easily effected to thereby instantaneously adjust the combustion stroke in accord with engine operational conditions. Indeed, the ECM can adjust the fuel and spark timing dynamically to each combustion chamber, thereby reducing or eliminating "knock", maximizing operating efficiency and minimizing pollutant emissions.
While dynamic control over fuel injection and spark timing are known and in widespread use today, there has been little done to implement dynamic control over valving. To date, most efforts in this regard have involved a drive linkage system which varies the rotation of a poppet valve cam shaft between two settings: retard and advance, which does not provide true dynamic control over valving.
Accordingly, what is needed in the art of fluid processing machines is fully dynamic control over valve events, including, duration and centerline thereof.